1. Field of the Invention
The present invention relates to a tracking (or steering) control circuit for an automatic guide vehicle (AGV). More particularly, it relates to a tracking control circuit for controlling the tracking of an AGV by an electromagnetic induction system.
This tracking control circuit for an automatic guide vehicle is based on Korean Patent Application No. 96-22414 which is incorporated herein by reference for all purposes.
2. Description of the Prior Art
An AGV is a load carrying vehicle that automatically follows a predetermined path. At an early stage of the AGV art, an optical guiding system, guiding the AGV's movement by applying a colored tape (often white tape) on a ground surface, has been used. However, if the colored tapes are polluted, there is a disadvantage that tracking of the AGV can not be adjusted due to the inability of a light-receiving section of an optical sensor to receive light reflected from the tape. Also, a guiding system using application of a magnetic tape has been used, however, analogous tape pollution problems may occur with such a system.
To solve the above-mentioned problem, an electromagnetic guiding system has been disclosed, which follows a predetermined path by sensing the intensity of an electromagnetic waves produced by a buried electric cable. As shown in FIG. 1, the cable 1 is buried under the ground surface, and a pair of induction coil sensors 2 for sensing the intensity of the electromagnetic wave are provided on the left and right sides of the buried cable 1, at a predetermined distance "a" from the buried cable. Accordingly, the tracking of the AGV is controlled by sensing the electromagnetic waves created by an alternating current flowing through the burial cable. A voltage level induced in one of the induction coils 2 has a characteristic that is inversely proportional to the distance between the cable 1 and the coil, such as that shown in FIG. 2.
When the electromagnetic guiding system is operating, however, the tracking control is achieved in a central processing unit (CPU) by repeatedly detecting a voltage difference at predetermined intervals between left and right induction coils (the voltage difference being dependent on the relative position of the induction coils with respect to the buried cable), and controlling the speed of left and right wheels of the AGV utilizing the detected value of the voltage difference and the speed of the AGV's movement.
However, the conventional tracking control system has the drawbacks that the processing time causes delayed due to heavy calculation requirement of the CPU, and that data must necessarily be converted into a format receivable by the CPU.